Phosphate Uptake and Its Relation to Arsenic Toxicity in Lactobacilli

Area of Science:

• Microbiology
• Environmental Science
• Toxicology

Background:

• Probiotic lactobacilli are explored for mitigating toxic metal exposure.
• Lactobacilli possess chelating and accumulating potential against cationic metals.
• However, their retention of anionic metalloids like arsenic is generally low.

Purpose of the Study:

• To investigate the role of phosphate transporters in arsenate [As(V)] uptake by lactobacilli.
• To explore the effect of phosphate-related gene mutations on arsenic resistance in lactobacilli.
• To understand the mechanism of arsenic biosorption and toxicity mitigation by probiotics.

Main Methods:

• Construction of mutants in phosphate transporter genes (pst) in *Lactiplantibacillus plantarum* and *Lacticaseibacillus paracasei*.
• Arsenate [As(V)] and arsenite [As(III)] uptake and toxicity assays.
• Analysis of the role of PhoP, a regulator of the PhoPR two-component system, in arsenic resistance.

Main Results:

• Phosphate transporters facilitate the incorporation of arsenate [As(V)] into lactobacilli, due to its structural resemblance to phosphate.
• Inactivation of the *phoP* gene in *Lc. paracasei* resulted in increased resistance to arsenite [As(III)].
• The *phoP* mutant showed no difference in As(III) retention or oxidation compared to the wild type, indicating specific transport mechanisms are key.

Conclusions:

• Specific transport, not general cell retention, is crucial for arsenate [As(V)] biosorption by lactobacilli.
• The study reveals an unexpected role for the pleiotropic regulator PhoP in arsenite [As(III)] resistance.
• These findings contribute to understanding probiotic-mediated detoxification of toxic metalloids.